User's Manual

Turbo PMAC PCI HRM
18 Main Board E-Point Descriptions
E3 - E6: Servo Clock Frequency Control
The servo clock (which determines how often the servo loop is closed) is derived from the phase clock
(see E98, E29 - E33) through a divide-by-N counter. Jumpers E3 through E6 control this dividing
function.
E3 E4 E5 E6
Servo Clock = Phase Clock
Divided by N
Default and Physical Layout
E3 E4 E5 E6
Location A4 A4 A4 A4
ON ON ON ON N = Divided by 1
OFF ON ON ON N = Divided by 2
ON OFF ON ON N = Divided by 3
OFF OFF ON ON N = Divided by 4 Only E5 and E6 On
ON OFF ON ON N = Divided by 5
OFF ON OFF ON N = Divided by 6
ON OFF OFF ON N = Divided by 7
OFF OFF OFF ON N = Divided by 8
ON ON ON OFF N = Divided by 9
OFF ON ON OFF N = Divided by 10
ON OFF ON OFF N = Divided by 11
OFF OFF ON OFF N = Divided by 12
ON ON OFF OFF N = Divided by 13
OFF ON OFF OFF N = Divided by 14
ON OFF OFF OFF N = Divided by 15
OFF OFF OFF OFF N = Divided by 16
Note: The setting of I-variable I10 should be adjusted to match the servo interrupt cycle time set by E98,
E3 to E6, E29 to E33, and the crystal clock frequency. I10 holds the length of a servo interrupt cycle,
scaled so that 8,388,608 equals one millisecond. Since I10 has a maximum value of 8,388,607, the servo
interrupt cycle time should always be less than a millisecond (unless you want to make your basic unit of
time on PMAC something other than a millisecond). If you wish a servo sample time greater than one
millisecond, the sampling may be slowed in software with variable Ix60.
Note: If E40 to E43 are not all on, the phase clock is received from an external source through the J4
serial-port connector, and the settings of E3 – E6 are not relevant.
Frequency can be checked on J4 pins 21 & 22. It can also be checked from the software by typing RX:0 in
the PMAC terminal at 10-second intervals and dividing the difference of successive responses by 10000.
The resulting number is the approximate Servo Clock frequency kHz.
E7: Machine Input Source/Sink Control
E Point and
Physical Layout
Location Description Default
E7
A6 Jump pin 1 to 2 to apply +5V to input reference
resistor sip pack; this will bias MI1 to MI8 inputs to
+5V for OFF state; input must then be grounded for
ON state.
Jump pin 2 to 3 to apply GND to input reference
resistor sip pack; this will bias MI1 to MI8 inputs to
GND for OFF state; input must then be pulled up for
ON state (+5V to +24V).
1-2 Jumper installed